Erstwhile signal for the 28th becomes a powerful implication astride the upper Mid Atlantic to SNE coasts.

[Typhoon Tip]

Time to raise awareness... at least than a week's notice

This is possible event is rapidly gaining ensemble support, while deterministic version appear to also be formulating a consensus for classic Miller-B cyclone evolution.  

These are the GFS (18z recent), the GGEM 12z, and the Euro also 12z...  c/o Tropical Tidbits.  The Euro doesn't carry ptype.... but it's all snow in this image almost down to the shores of the south coast of SNE. These are on the 28th... and don't show the potential quite as far as it can go as a rapid deepening storm type - keeping in mind, we are just formulating consensus. These next several model cycles will be interesting to say the least.

Basic synopsis:  Primary low climbs toward S. Ontario/St L. Seaway...but runs into a retrograde/transitive exertion from an intensifying negative mode of the North Atlantic Oscillation.  The mid and upper air charts as that is occurring then abandon that primary circulation, as the S/W(s) mechanics are forced to dive toward the Del Marva to NYC latitude along the EC - where the canonical explosive baroclinicity resides with the cold continent air ( enhanced by antecedent cold high pressure stalling N. of Maine, also a manifestation of the -NAO/confluence) is proximal to the Atlantic Ocean

This changing hemispheric circulation mode is as follows,

.. Thus, this is an "index-scale" driven event, one where well-timed disturbance gets "caught" in the instability/restoring along the inflection of that diving curve you see above.   We typically find that bigger events are tied so such changes, and often do gather into consensus rather early across guidance pantheon. The reason for that is because the physics of such large, titanic forces have a lot of momentum once they begin to "move", and are thus less susceptible to "noisy" perturbation, that can and do often cause the typical deterministic headaches we deal with with more sub-index events ...that that seldom survive 7 days of model permutation...etc.  

Aspects to watch for:    the amount of phasing with trailing S/W mechanics is in question. The Euro has more of that, such that it's sfc result is deeper and more violent implicated along eastern New England. However, all three suggest a solid moderate/borderline major snow amount, without the monster solution of the Euro.  I have seen some snow charts for the Euro model that are ...quite obscene but I'll leave those to y'all to entertain this thread with some of that...  

What is also not present here is the PNAP pattern.  The Euro has more of a transient +PNAP structure ejected through the west then does the GFS and GGEM.  That may be why-for it features more phasing with trailing mechanics.   Though this event is inside of D6, it is still not quite in the the better model performance range.  It's damn close!   It is possible that the these other guidance may come around, or...the Euro may go toward less.

Also, this event may slow down it's departure in future runs - but that's very speculatively based upon uncertainty as to how the downstream flow continues to "back exert" and slow down the 'atmospheric traffic' - so to speak.   

[Typhoon Tip]

Sorry I didn’t realize that there was already a thread running for this. 

[HIPPYVALLEY]

1 minute ago, Typhoon Tip said:

Sorry I didn’t realize that there was already a thread running for this. 

Hopefully a moderator combines them so your write is in the discussion.